I have seen some leftists stand by this statement as entirely true, and I have also seen some leftists dismiss this idea as cope on the part of liberal Zionists who dislike Netanyahu/Likud (and who would like to delegitimize both Likud and Hamas together).
The following are some relevant articles that support this idea:
https://theintercept.com/2018/02/19/hamas-israel-palestine-conflict/
https://www.thenation.com/article/world/why-netanyahu-bolstered-hamas/
What is clear is that Israel has allowed Qatar to fund Hamas on numerous occasions without much interference. However, whether Israel has ever actually funded Hamas specifically with Israeli money is not as well-established (although many of the people who support the general “Israel propped up Hamas” idea definitely imply that this has happened). So as a corollary question, how important of a difference is this?
I remember seeing an interview with an ex Israeli intelligence guy who admitted that they funded Hamas in the beginning. It’s probably true but it’s not a good talking point imo since it leans heavily into the “both sides bad” trope.