The United States has now partly outsourced their intelligence gathering to BigTech and has also made laws to compel any tech companies to allow them to tap into any business network (see Why Lavabit shutdown? - https://it.slashdot.org/story/14/05/20/2143258/why-lavabit-s... ) with whom they don't have an explicit arrangement. So it is important to note that your actions may be helping US / 5-eyes / 9-eyes intelligence agencies.
This is important to keep in mind as you are being asked to take sides in an international conflict and help circumvent the laws of one country. And this may have negative repercussion for you in the future. For example, you don't have any guarantees that Signal will not use these proxies for other countries too, and that could create legal trouble for you in your own country if they have a good relation with the country whose communication network / laws you are helping to circumvent. Or, you may become a person of interest in Iran or other countries for doing this and be a potential target for them which can create legal difficulties for you in the future; international travel can become difficult for you. (Yes, I am outlining the worst-case scenarios).
I write this because I too was once naive about how the Internet would change the world by making information open and accessible to all and bring us all closer with the ability to freely communicate through it.
The reality today is a lot more sobering - the internet has been siloed and while information technically is still freely available it's very controlled, it is being used to profile people at a massive scale, experiments are being done through social networks to use them to deliberately create social and political turmoil in many countries, platforms like Wikipedia and Google Maps or Open street maps are being increasingly used to entice naive people to share and make even more information public without understanding the repercussion of how it may be used against their country, and worst of all, attempts are being made to replace your own country's communication network with it ...
So go ahead and do this if you believe it will do political good, but do it it with your eyes open.
I'll end by pointing out that Signal is also one of the new controlled silos of the internet and not an open or distributed platform like the internet was originally envisioned by some.