DTLS solves the first problem by banning stream ciphers.
From this, i concluded that the use of CHACHA20 (a stream cipher) would not work in DTLS.
However, from both looking at the source code in rustls, the IANA canonical list of cipher suites, and at RFC 7905, using CHACHA20 looks to be possible, as rustls plugs in sequence numbers into both algorithms just the same.
RFC 6347 Section 3.1 mentions the following;
From this, i concluded that the use of CHACHA20 (a stream cipher) would not work in DTLS.
However, from both looking at the source code in rustls, the IANA canonical list of cipher suites, and at RFC 7905, using CHACHA20 looks to be possible, as rustls plugs in sequence numbers into both algorithms just the same.