Cloudflare’s CAPTCHA is Turnstile. I’ve found it very useful. It doesn’t use pick the image or type the text, it’s just tick the box. You can even set it to invisible, then the user doesn’t need to even do that, the challenge is sent to the browser and is completed automatically.
https://developers.cloudflare.com/turnstile/
In terms of privacy, it’s is still Cloudflare, but at least it’s not intrusive to the user experience.
Yes, both SL and addy.io have the feature to enable/disable individual addresses.
I highly recommend crDroid. It’s super customizable and has a good battery life / performance ratio.
You have to add the FUTO repo https://app.futo.org/fdroid/repo/