I use ColorNote since ages. It's very simple, it allows to create checklists and notes. It can also use Google Drive as backup storage. Trello and Google Keep are also good tools. There is also Evernote. But I still don't get used to it.

I have used a few in the past, but fabulous recommended using the old fashioned note book and pen and google calendars. That’s what I have been doing, and it serves me well. Writing your task has a different sense of accountability than typing. It helps to stay on track.

I use Todoist as my general to do list. It is very clean looking and allows for time and location reminders. Plus it works on all platforms.
For more detailed work I have discovered Notion. It allows more flexibility than trello, as you can do the kandan boards, but also switch to tables, list, cards, etc; all while using the same source data. I am running my dissertation research out of it! It is free but there are is also a premium version for like 4 bucks a month. This a link for Notion if you want to try it you get $10 and I get $5 in app credit. (I am not related to the company, I am a just graduate student.) https://www.notion.so/?r=bf1298660bf14e468435d26a76d11de4

I use Stuff application for to-do list. It's simple, and it shows the essentials only. No ads. The widget shows to-do list for today, tomorrow (which can automatically turn to be today's to do list), and upcoming days (for me to give reminders and deadlines). It has strike through feature so I can see how far I make my way towards my plans.

I use Wunderlist. Very easy and organized. Also makes little ding noises if you want when you check something off. The deleted items save so if you have something like a packing list, you can always bring items back for the next time you pack since you usually need most of the same things.