Google unfortunately locks down the RCS api's in Android so that only the system messaging app (basically just Google Messages these days) can use them, so I don't think any independent messaging apps can integrate RCS at all :/
Unfortunately I haven't run across any either :/ Handwriting detection for even a single language/script can be very complicated to implement so I understand why it's rare in open-source keyboard options, but I'll keep an eye out just in case I find one.
Windows now handles 7z files natively too (at least as of the upcoming Windows 11 24H2 version), I'm glad they've at least added some legit new features for File Explorer.
I believe they actually adopted it for their Tizen OS, unless I completely invented that memory.