[horde] Query re Horde and php 8.0 and 8.1

[info at interpost.biz]

  Hello,

We tried upgrading horde 5 Groupware Webmail edition (latest release  
from debian 10 channels) to php 8.0 adn 8.1 today and it failed  
miserably.

Is this software (Groupware 5 Webmail edition) compatible with php 8.0  
or 8.1 ?

Do we need to get it elsewhere  (for example back to pear/pecl  
install) to get a version compatible with php 8.x ? (other than debian  
maintainers ..;)

Is  a composer install workign and php 8.x compatible?

Is there a timeframe for php 8.x compatibility?

Thanks,
 

  Ed