Unable to connect from iOS to Bazzite using RDP

I have problems connecting Mocha RDP Lite (iOS) to krdpserver (Bazzite). Here is what the server log shows me when NLA authentication is enabled in RDPLite, which is the default setting:

# NLA enabled
krdpserver[3535]: [12:36:23:977] [3535:0000570b] [ERROR][com.freerdp.core.nego] - [nego_read_request]: Incorrect negotiation request type 13
krdpserver[3535]: [12:36:23:977] [3535:0000570b] [ERROR][com.freerdp.core.peer] - [peer_recv_callback_internal]: CONNECTION_STATE_NEGO - rdp_server_accept_nego() fail
krdpserver[3535]: [12:36:23:977] [3535:0000570b] [ERROR][com.freerdp.core.transport] - [transport_check_fds]: transport_check_fds: transport->ReceiveCallback() - STATE_RUN_FAILED [-1]

I tried disabling NLA authentication, which leads to the following error messages:

# NLA disabled
krdpserver[3535]: [12:47:54:605] [3535:0000582f] [ERROR][com.freerdp.core.nego] - [tpkt_ensure_stream_consumed_]: [nego_read_request] Received invalid TPKT header length 13, 2 bytes too long!                                             
krdpserver[3535]: [12:47:54:605] [3535:0000582f] [ERROR][com.freerdp.core.peer] - [peer_recv_callback_internal]: CONNECTION_STATE_NEGO - rdp_server_accept_nego() fail                                                                      
krdpserver[3535]: [12:47:54:605] [3535:0000582f] [ERROR][com.freerdp.core.transport] - [transport_check_fds]: transport_check_fds: transport->ReceiveCallback() - STATE_RUN_FAILED [-1]                                                     
krdpserver[3535]: [12:47:57:803] [3535:0000583e] [ERROR][com.freerdp.core.nego] - [tpkt_ensure_stream_consumed_]: [nego_read_request] Received invalid TPKT header length 13, 2 bytes too long!                                             
krdpserver[3535]: [12:47:57:803] [3535:0000583e] [ERROR][com.freerdp.core.peer] - [peer_recv_callback_internal]: CONNECTION_STATE_NEGO - rdp_server_accept_nego() fail
krdpserver[3535]: [12:47:57:803] [3535:0000583e] [ERROR][com.freerdp.core.transport] - [transport_check_fds]: transport_check_fds: transport->ReceiveCallback() - STATE_RUN_FAILED [-1]

I wonder what is causing these problems? Unfortunately I have not yet found an alternative to RDPLite which I could try, so I don’t even know if the problems are specific to this particular client software.

Pointers and suggestions would be appreciated.