Thompson wrote: I probably have ad blockers on Brave and Chrome ok. They don't stop me using YouTube or various other media sites.

The difference is that this site downloads the whole file, all 2MB of it, and then plays it - in Firefox anyway. YouTube and similar stream media files - download it in small sections as it plays.

I suppose the BL do that because the sound clips are short and of low quality.

I found that uBlock Origin on Android blocks by default media files greater than 50KB; I can change the limit by website. I expect other ad-blockers do the same, though I'm not sure why.

My guess is that if the site blames Flash for not playing then you do have Flash installed.