Trusted, non custodial, supports PIN or passwords to unlock, and no bugs.
Electrum meets these criteria. Other commonly used Android wallets include Mycelium and Schildbach wallet.
All three of these are also open source and reproducible:
https://walletscrutiny.com/#tableofwallets3. The only DEX I have read about is BISQ. I know nothing about it except that some consider it too difficult and overcomplex to use. Is there something else where I could convert my bitcoin to tether if I need tether? Only good DEXs please. I have had accounts being locked for months on popular exchanges and I dont want that again. Even if I want to trade live with people maybe it is not a bad idea to be able to withdraw USD or EUR from a DEX if possible to my own bank account. Do they work like that?
Bisq will certainly let you trade your bitcoin directly for USD or EUR, provided you can find someone to trade with. There is no denying that Bisq is somewhat more complex to use than a standard DEX, but it is also the more secure and private. There are some pretty in depth guides on how to use it available on their Wiki:
https://bisq.wiki/Main_PageOther good DEXs which support fiat trades are AgoraDesk or RoboSats.