Trying to get decent creamy ice cream with old machine

Hello everyone (sorry if double posting, I think something went wrong with my previous post),

tldr; Can I adapt the recipe I used so it is creamier and softer without having to add condensed milk or sugar? If not, how to adapt by adding only condensed milk?

I recently decided to get back to making ice cream using my mom's old school "sorbetiere" (brand is SEB, see first image) which, I am sure you are already familiar with it, is basically a churning device you put directly in the freezer while plugged outside. and you wait. For reference, I had not used it for over 20 years. Back in the years, I used it mostly for making sorbet.

This time, I tried a matcha ice cream recipe with the following ingredients:

200 ml whole milk, 200 ml 33% cream, 2  egg yolks, 75 g sugar, 1 tsp cornstarch,1.5 tbsp matcha powder. Basic custard recipe, then cool it down and put it in the sorbetiere in the freezer.

but as far as I was (very) happy with the taste, I was (very) unhappy with the texture.

Basically, my main observations are as follow:

• the custard took HOURS to start to solidify/become thicker. Like possibly over 5hours to start to get something ice-creamy like
• But, eventually, the ice cream was EXTREMELY hard once frozen.
• Note that I tried twice (with same custard). First time, I had not found the red cover and thought that maybe there was something wrong going on because of it. But it ended up resulting the same
• Note that I am also relatively confident the problem is not from the cooking of the custard (I make some very very frequently).
• Note that the bowl of the turbine is foil only, no thermic liquid in it. But I had put it in the freezer for 24hours before to start the turbine, had waited for the custard to cool down, etc. etc.

I therefore started to investigate where the problem might have came from. I found this fantastic subreddit and also found a link to the ice cream calculator that I used to check what it would say about the recipe I used. And basically it said that it was definitely on the "hard side" (see second image). So I guess it made sense.

My question is as follow: could my result be expected from the recipe, and if yes, how can I adapt the recipe without adding condensed milk or sugar to get a creamier/softier ice cream ?

Thanks in advance