It’s all in the title: I installed Adguard Home. I use admin/dietpi as login/passwd; Error: control/login | invalid username or password | 403
This page is wrong : DNS Servers Options - DietPi.com Docs
Then, login to the web UI e.g. athttp://<your.IP>:8083 as admin using the root user’s password.
nope. fully correct. admin password is the global software password and not the root user password. These are 2 different passwords. Most probably you changed the global software password during DietPi installation. Majority of user uses the same for root and global software.