I use ublock origin in Librewolf configured with Blocking mode: medium mode. As this mode blocks all 3rd party scripts and frames by default there's a lot of login sites that don't work because the use of captchas, so after some internet searching I've managed to make it work with following configuration in uBO my rules.
You can replace * for a specific domain rule.
recaptcha
* https://www.google.com/recaptcha/ script noop
* https://www.google.com/recaptcha/ sub_frame noop
* https://www.gstatic.com/recaptcha/ script noop
* https://www.recaptcha.net/recaptcha/ script noop
* https://www.recaptcha.net/recaptcha/ sub_frame noop
hcaptcha
* https://hcaptcha.com/1/api.js script noop
* https://newassets.hcaptcha.com/c/ script noop
* https://newassets.hcaptcha.com/captcha/ script noop
* https://newassets.hcaptcha.com/captcha/ sub_frame noop
I've identified some sites that use other captchas
dropbox
www.dropbox.com dropboxcaptcha.com * noop
aliexpress
login.aliexpress.com https://cf.aliyun.com/nocaptcha/ script noop
If you have other configs you can share here.
What do you mean with "anonymous login"? If you need to create an account, then it's not anonymous.