Here’s my personal list of recommended apps for a few things:

• Aegis (Play Store / F-Droid / GitHub) - 2FA FOSS app that’s minimal and simple
• Auxio (F-Droid / GitHub) - No-nonsense music player for local files
• ConnectBot (Play Store / F-Droid / GitHub) - Simple SSH client
• K-9 Mail, soon to be Thunderbird (Play Store / F-Droid / GitHub) - No-nonsense e-mail client
• NewPipe (F-Droid / GitHub) - YouTube client for privacy, has no ads, supports background playing, local subscription lists, and ability to download videos
• Techmino (GitHub) - FOSS Tetris clone with no ads and multiple modes, definitely my favourite
• Waistline (F-Droid / GitHub) - Calorie counter app that stores all data locally. Need to add products yourself but have full control.