I’ll start by asking the same questions as here: SSL Certificate of https://mein.elba.hypo.at/ is not accepted on desktop Win11 - #2 by JimB1
Also, the cert error text is clickable. If you could include a screenshot after having clicked that, the content it reveals may be helpful.
For clarity, has this issue ever occurred when your Kaspersky software was disabled? (It’s great that you caught onto the various Avast issues people have had.)