How does rspamd is being logged to delivery logs on your end? I'm using SM beta only as incoming gateways where main SM is stable version but still IMHO delivery logs from incoming gateway should contain some rspamd reference. Take a look at example delivery log spam entry:
2022.12.28 20:40:19.200 [69778845] Spam Check results: [REVERSE DNS LOOKUP: 0,Passed], [NULL SENDER: 0,passed], [_SPAMASSASSIN: -4:-5], [_REMOTERSPAMD: 0:1], [_SPF: 0,Pass], [_DK: 0,None], [_DKIM: 0,Pass], [ANONMAILS: 0], [VIRUS RBL - MSRBL: 0], [SPAMRATS - DYNA: 0], [MAILSPIKE BL: 0], [BACKSCATTER: 0], [UCEPROTECT LEVEL 3: 0], [UCEPROTECT LEVEL 1: 0], [SPAMHAUS - CBL: 0], [GBUDB: 0], [BARRACUDA: 0], [UCEPROTECT LEVEL 2: 0], [SURRIEL: 0], [MAILSPIKE Z: 0], [CBL - ABUSE SEAT: 0], [SORBS - SPAM: 0], [SORBS - NEW: 0], [SPAMRATS - SPAM: 0], [SORBS - ABUSE: 0], [SORBS - SMTP: 0], [HOSTKARMA - BLACKLIST: 0], [URIBL BLACK: 0], [SEM-URI: 0], [SURBL: 0]
2022.12.28 20:40:19.200 [69778845] Spam Checks completed.