Some people are uncomfortable with the word s3x (seks), others just want a monolexic label. Here are some alternatives, based on dyadic given that the problem was with its prefix, not the suffix:

Prot(o)sex – protadic

Var(i)sex – variadic/varadic

Par(a)sex – paradic

Endosex – endadic

Perisex – periadic

Juxtasex – juxtadic

Intersex – interadic

Altersex – alteradic

Cissex – cisadic

Ultersex – ulteradic/ultradic

Citersex – citradic/citeradic

Ipsosex – ipsadic/ipsoadic

Transsex – transadic/tranadic/trannadic

Intrasex – intradic

(Am)bissex – (am)biadic

Polyssex – polyadic/poliadic

Multissex – multiadic

Plur(i)sex – pluradic/pluriadic

Extersex – exteradic/extradic

Infrasex/infersex – infradic/inferadic

Altsex – altadic

Teresex – teradic/nulladic/nuladic

Duosex/duasex – duadic/duoadic

Diversex – diveradic/divradic

Phantasex – phantadic/fantadic

Binisex – binadic/biniadic

Peransex – peradic/peranadic/perandic

Trissex/trisex – triadic/teradic

Liberasex – liberadic/libradic

Sexflux – fluxadic/flexadic

Sexfluix – fluixadic/fliuxadic/flinadic

Metasex – metadic

Isosex – isadic/isoadic

Vaguesex – vaguadic

Apasex – apadic/cassadic

Faunasex – faunadic

Florasex/florsex – floradic

Xenosex/xensex – xenadic

Sexpunk – punkadic/punxadic

Neutersex – neutradic/neuteradic

Antersex/iltersex – iltradic/antradic/anteradic/ilteradic

Mythosex – mythadic/mitadic/mytadic/mytholadic/mitoladic

Monstersex/teratosex – monstradic/monsteradic/teratadic

Apothisex – apotiadic/apotadic/apothadic/apothiadic

Assex/ansex/asex – anadic/unadic/aydic/ayadic/aiadic

Nbysex – enbadic/enbyadic/enbiadic/nbadic/nbyadic/nbadic/nonbadic/nbiadic

Pansex – omnadic/onadic/omniadic/oniadic/panadic/pandic

Sexqueer/queersex/cuirsex/kuirsex/kweersex – queeradic/cuiradic/kuiradic/kweeradic

Astersex/astrosex/astrasex – astradic/asteradic

Amplussex/amplisex – ampladic/amplusadic/ampliadic

Grayasex/greyasex – greyadic/grayadic/gradic/graydic/greydic/grisadic

Othersex – oteradic/oradic/outradic/outeradic/outheradic/otheradic/eladic/eliadic/outhradic/othradic

Demissex/hemisex/semisex – semiadic/semadic/demiadic/demadic/hemadic/hemiadic