I didn't know what a SaaS affiliate program was until recently. Still researching, but here is our shortlist #buildinpublic

https://www.promotekit.com/
Free tier to start, then $39/mo ➡️ $10k/mo in referrals

https://tolt.io
$29/mo ➡️ $2.5k in referrals
$49/mo ➡️ $7.5k

https://www.rewardful.com
$49/mo ➡️ $7.5k in referrals