I'm unable to get this to work on Elgg 4.1.1

For example if a page has a text to Vimeo URL, I get fatal error:

#0 /home/customer/www/mydomain.com/public_html/mod/oembed/classes/ColdTrick/OEmbed/Process.php(378): serialize(Object(Embed\Adapters\Vimeo))
#1 /home/customer/www/mydomain.com/public_html/mod/oembed/classes/ColdTrick/OEmbed/Process.php(323): ColdTrick\OEmbed\Process->cacheAdapter('https://vimeo.c...', Object(Embed\Adapters\Vimeo))
#2 /home/customer/www/mydomain.com/public_html/mod/oembed/classes/ColdTrick/OEmbed/Process.php(214): ColdTrick\OEmbed\Process->getAdapter('https://vimeo.c...')
#3 /home/customer/www/mydomain.com/public_html/mod/oembed/classes/ColdTrick/OEmbed/Process.php(183): ColdTrick\OEmbed\Process->replaceUrl('https://vimeo.c...')
#4 [internal function]: ColdTrick\OEmbed\Process->ColdTrick\OEmbed\{closure}(Array)
#5 /home/customer/www/mydomain.com/public_html/mod/oembed/classes/ColdTrick/OEmbed/Process.php(192): preg_replace_callback('~(?xi)\n ...', Object(Closure), 'https://vimeo.c...')

ETC...

If I whitelist vimeo on the OEmbed settings, I don't get fatal error. But then the OEmbed doesn't seem to do anything at all to vimeo's URL-texts. The same problem repeats with youtube...

@Stuart

I'm unable to reproduce the issue. I have no problems embedding YouTube, Vimeo or Twitter.

You didn't include the actual error message in your log sample. It should be just above where the backtrace (with all the #0-9 begin)

@Stuart,

We were able to reproduce the issue on a PHP 8+ installation.

We created a fix which is available on GitHub/Packagist or wait until the next release.