In article
.com,
says...

As a Fujifilm shooter I have my X-T3 combined with the XF 100-400mm f/4.5-5.6 OIS WR, and an X1.25TC.

That does not quite deliver the benefit of a constant aperture f/4.5, but my combo is weather resistant, and affordable until Fuji delivers additional, long, fast wildlife glass other than their non-zoom XF 200mm f/2.

The X-T4 would give IBIS, which can make quite a difference in
some situations.
--
Alfred Molon

Olympus 4/3 and micro 4/3 cameras forum at
https://groups.io/g/myolympus
https://myolympus.org/ photo sharing site