There's a new streaming service called "Frndly" that costs $5.99 a month, or $7.99 a month for HD and DVR. Their lineup contains GSN, Hallmark, the Weather Channel, and a few others. Supposedly family friendly, but don't tell that to the 10 hours of Harvey Feud airing on GSN daily.
If you don't have GSN, this is probably the lowest-cost streaming option available. The next closest is probably Philo, which has 58 channels for $20/mo, including GSN.
https://www.frndlytv.com/Personally, I've been on the YouTube TV bandwagon for a few months now, and am very happy with the service. This Frndly service fills in some gaps with missing channels on YouTube TV...but not worth it to me to pay $6/mo for GSN unless they bring back some classics.