It really depends on who your friend is, and who they are trying to defenf against.

If the US ( or Russian / Chinese) government really wants to access an internet-connected device, they can do it; what app you are using doesn’t even matter. For example, most people use the default Google keyboard, which could be compromised.

If the concern is about local goons / employers / coworkers, then both Telegram and Signal are more than enough to stop them prying.

As for whether to use Signal or Telegram, Signal has end to end encryption enabled by default, while in Telegram you have to switch it on for each chat. On the other hand, Telegram has the best UI among messaging apps hands down.

Debian already has an ARM version. Do you mean some Qualcomm drivers are missing? There are already Ubuntu ROMs for Android phones, so this shouldn’t be an issue, right?

It messes up object arrangement. This is technically Microsoft’s fault, but that doesn’t help when you want to communicate clearly with a MS Office user.

LibreOffice has more features and is overall better. OnlyOffice is more compatible with MS Office. So if you need to use docx etc. for work, you use OnlyOffice as a workaround.

When modern-day Ukraine was formed in 1990, it was majority Ukrainian, but with a sizable Russian (and smaller Romanian and Polish) minority. Over the next twenty or so years, this minority voted for parties and politicians that favoured stronger ties with Russia. In contrast, ethnic Ukrainians supported joining (or at least aligning with) the EU. This conflict came to a head in 2014, when the pro-Russian government was overthrown by pro-EU protestors. Relations between the two groups have worsened since then, leading to pro-Russian militants seizing power in the (Russian majority) Donbass and Crimea, and joining Russia.