Any SIP phone meeting the basic technical requirements can be connected to your Bitrix24. There are lots of models of such phones, and it is extremely difficult to test all of them with Bitrix24. Here's a list of tested SIP phones:
DECT telephones can be connected via SIP gateway (VoIP SIP adapters). The work with Linksys PAP2T successfully passed the test.
Also, it is possible to use the telephony with softphones for Windows, iOS, Android: Media-5, Zoiper, CSipSimple, etc.