In terms if logging: sys journal does the job for me …
I do run prometheus + grafana for some services but that is mostly for some fancy looking graphics nothing really usefull.
I would recomend you to monitor updates of you apps so you are well informed when und what to update (i just have subsribed to all the diffrent release git rss feeds)
Hm, nextcloud and DavX5 are crucial for me (file, calendar and contact sync)
Also Aegis as 2FA client and KeePassDX as PasswordManager (both synced via nextcloud)
I wont list all the messengers ^^’