Apps I use on N900 in 2022:

Telegram: MPGram (lightweight Telegram web client) and Telegram-cli from Extras-devel (CLI solution). Here is icon and shortcut I created (adds icon to apps menu).

Browser: I like built-in MicroB most. It's fast, renders pages well and works well with Nginx tweak. Opera Mobile for more features like selecting text.

E-mail: Built-in client. Supports Gmail and Yandex with manual settings and app password. Also MicroB can open old HTML version of Gmail and displays it really well (you will need stylus for comfortable browsing though )

Camera: BlessN900

RSS: FeedingIt is great app, loads most of feeds for me.
If you can't load feed because of lack of TLS 1.2/1.3 - add http://nnp.nnchan.ru/glype/browse.php?u= before feed URL, it will make feed processed by proxy.

Maps: Nokia Maps with maps downloaded from http://nokiamaps.ct8.pl. Use version 00.01.29.100.
Sygic Mobile Maps is second option. How to install -> https://t.me/maemomeegoapps/77

Kernel: last Kernel Power, battery patch and power patch.
That overclocks N900 to 805 MHz.

Bootmenu: U-Boot, it allows me to have three systems.
https://talk.maemo.org/showthread.php?t=101338

Music player: SomePlayer, works much better than default for me.

Video player: SMPlayer / mplayer. SMPlayer is basically front-end for command-line mplayer.

YouTube: JTube (YT client for Java ME working via phoneME emulator, supports only downloading videos)
https://openrepos.net/content/wunderwungiel/jtube
And iteroni.com as light YouTube front-end (Invidious instance).

MMS: fMMS should be solution, but it doesn't work for me with correct settings