SSL_ERROR_RX_RECORD_TOO_LONG
I made a certificate using mkcert -install. I then went to https://localhost:8080, using the test webserver I was running. It worked with http://localhost:8080, but not with https://localhost:8080. It gave me the error SSL_ERROR_RX_RECORD_TOO_LONG. I have attached a screenshot.
It seems like the SSL certificate was successfully created though, I have also attached a screenshot.

Having the same issue. I am generating the certificate from a dockerized Ubuntu 20.4 and my host system is Manjaro Linux. I am using mkcert 1.1.2. Also tried 1.4.3
Same here using 1.4.3 in Ubuntu 20.10 with Apache 2.4.46. I followed the instructions from Chandan Kumar and had no errors until trying to actually load in Firefox.
Also have this issue. mkcert version 1.4.3; mac osx 11.6 (20G165); Firefox Developer Edition 94.0b4 (64-bit)
yep, same problem on windows 10 and ff 75.0.2 . i have built from source(go). last commit was in february.