In my experience non UST tyres on converted rims are near on impossible to get to seal
In my experience it’s a complete lottery. Some go on fine, some don’t. In the end it frustrated me to the point of chucking the whole f***ing lot (tyre, wheel and track pump) into the field behind our house and reverting to a tube (once I’d got it all back out of the field!). I’m pretty sure the tyre I was trying to put on was identical to the one I’d taken off (which had gone on fine, never leaked but was worn out). I don’t deal well with failing at something and knowing that my only option is to try the ame thing again and hope for a different result.
Having said all this… I am starting to think again about going (converted) tubeless again. I guess time has dulled the pain.