u/Alternative-Day-9470

Some of us have been changing and trying multiple custom firmware, and it leaves marks (many folders and residual files).

Is there a safe way to just wipe everything and start clean?

So, if I format the SD card, what should I do next?

I usually use epubkit to optimize EPUB files since it seems to be the most thorough EPUB optimizer tool I've seen. I just checked a few minutes ago and it's not accessible? No... Any recommendations for similar tools that can do a thorough job?

FYI, it does 20 step job

Step	What it does
1	DRM check — detects DRM-protected files and stops early with a clear message
2	Extract — unpacks the EPUB ZIP structure into a working directory
3	Parse structure — locates the OPF package file and parses the manifest
4	Read metadata — extracts title, author, series, language, cover reference
5	Apply metadata edits — overwrites title/author if the user edited them in the UI
6	Find content files — catalogs all XHTML, CSS, image, and font files in the EPUB
7	Process images — converts all images to baseline JPEG, resizes to the device screen (480x800 for X4, 528x792 for X3; max 1024x1024), applies 4-level grayscale quantization with Floyd-Steinberg dithering, autocontrast histogram stretching, and contrast boost. Light Novel mode rotates/splits landscape images
8	Fix SVG covers — unwraps SVG-wrapped cover images (common in Gutenberg/store EPUBs)
9	Generate cover — creates a title/author cover image if the book doesn't have one
10	Update references — rewrites all internal hrefs and srcs to match renamed image files
11	Repair HTML + strip attributes — fixes malformed XHTML with lxml recovery parser, strips unnecessary attributes (data-*, aria-*, role, tabindex, etc.) to reduce parsing overhead for the 380KB RAM device
12	Remove unused CSS — collects all used classes/IDs/elements across XHTML files, then strips CSS rules that don't match anything
13	Remove embedded fonts — deletes u/font-faceStep What it does1 DRM check — detects DRM-protected files and stops early with a clear message2 Extract — unpacks the EPUB ZIP structure into a working directory3 Parse structure — locates the OPF package file and parses the manifest4 Read metadata — extracts title, author, series, language, cover reference5 Apply metadata edits — overwrites title/author if the user edited them in the UI6 Find content files — catalogs all XHTML, CSS, image, and font files in the EPUB7 Process images — converts all images to baseline JPEG, resizes to the device screen (480x800 for X4, 528x792 for X3; max 1024x1024), applies 4-level grayscale quantization with Floyd-Steinberg dithering, autocontrast histogram stretching, and contrast boost. Light Novel mode rotates/splits landscape images8 Fix SVG covers — unwraps SVG-wrapped cover images (common in Gutenberg/store EPUBs)9 Generate cover — creates a title/author cover image if the book doesn't have one10 Update references — rewrites all internal hrefs and srcs to match renamed image files11 Repair HTML + strip attributes — fixes malformed XHTML with lxml recovery parser, strips unnecessary attributes (data-*, aria-*, role, tabindex, etc.) to reduce parsing overhead for the 380KB RAM device12 Remove unused CSS — collects all used classes/IDs/elements across XHTML files, then strips CSS rules that don't match anything13 Remove embedded fonts — deletes u/font-face rules from CSS, removes font files (.ttf, .otf, .woff, .woff2), and cleans them from the OPF manifest14 Normalize whitespace — strips excessive empty paragraphs/divs, adds CSS page-break-before to chapter headings (h1, h2)15 Text cleanup — scans all text nodes (skipping script/style/pre/code) and fixes: double spaces, OCR ligature artifacts (fi/fl/ffi/ffl/ff), smart quotes → straight quotes, mojibake encoding errors, punctuation issues, Unicode NFC normalization16 Clean metadata — strips store-specific tags (Calibre, iBooks, Kindle, Amazon, Google Play, Kobo)17 Fix TOC — validates the Table of Contents, generates one from chapter headings if missing18 Clean OS artifacts — removes .DS_Store, Thumbs.db, __MACOSX, desktop.ini, etc.19 Repackage — rebuilds the EPUB ZIP with correct mimetype entry and deflate compression20 Output filename — generates a clean Author - Title.epub filename from metadata rules from CSS, removes font files (.ttf, .otf, .woff, .woff2), and cleans them from the OPF manifest
14	Normalize whitespace — strips excessive empty paragraphs/divs, adds CSS page-break-before to chapter headings (h1, h2)
15	Text cleanup — scans all text nodes (skipping script/style/pre/code) and fixes: double spaces, OCR ligature artifacts (fi/fl/ffi/ffl/ff), smart quotes → straight quotes, mojibake encoding errors, punctuation issues, Unicode NFC normalization
16	Clean metadata — strips store-specific tags (Calibre, iBooks, Kindle, Amazon, Google Play, Kobo)
17	Fix TOC — validates the Table of Contents, generates one from chapter headings if missing
18	Clean OS artifacts — removes .DS_Store, Thumbs.db, __MACOSX, desktop.ini, etc.
19	Repackage — rebuilds the EPUB ZIP with correct mimetype entry and deflate compression
20	Output filename — generates a clean Author - Title.epub filename from metadata

I slap a hydrogel screen protector on every gadget I have in my household. The seller can usually cut it as I ordered since the gadget brand is well known. Smartphones, tablets, iPads, iPhones, Nintendo devices—everything they are capable of cutting to the right size. Yet when I ask for XTEINK, they say they don't have the template. Such a shame.

Taobao and other overseas e-commerce sites aren't a good option from a money and time perspective. I'm thinking of custom-cut hydrogel from the brand I trust, which is always my first choice, as at $2, it has already done an exceptional job and is of good quality.