I’ve enjoyed using the Simple Alarm Clock on F-droid, importantly for me, it requires you to hold down the shut off button for a couple seconds which helps prevent me from accidentally shutting off my alarm instead of snoozing it. Only downside for this app and possibly others is that they may not function if your device OS updates in the middle of the night.

Sounds like your best bet is to self host an email service

I have had success with the Simple Alarm Clock on F-Droid (not to be confused with the simple mobile tools apps). It has necessary basic features like custom alarms, increasing volume, and dismissing the alarm requires holding down “dismiss” so the chances of accidentally dismissing an alarm instead of snoozing it are much lower. The only time it seemingly failed me was after an overnight android update (samsung), where it didn’t work until the phone was unlocked.

Armcord is good and uses Vencord as well for plugins/theming. Webcord is another option that is primarily privacy-focused