How and where to save the archive of RSS feeds from the RSS feeder of the old Opera (Presto)?

Question

Opera

Hello.
There is an old Opera 12.17 and it has an RSS feeder with an RSS archive for a couple of years, which I really don’t want to lose.
It is long overdue to switch to a new browser.
Q: Where can I save the RSS archive?
The PC has Thunderbird, it seems like it also understands RSS and even has a similar storage format. I tried to unload RSS into it by the method of small-scale mechanization - it turns out porn (each of the many thousands of RSS falls into a separate folder and Thunderbird dies).
Does anyone have a working conversion solution?
Perhaps there are some options besides Thunderbird?

Answer 1

The Opera website has a separate RSS reader + Mail client "bitten* from the old Opera.
It is clear that it is unlikely to be updated, but...