I have seen multiple videos about integration of Amazon Alexa into Home Assistant (or the other way around). There is the unofficial way via HACS and putting your credentials into config files within HA and there is NabuCasa, which is a paid subscription service from the developers of HA.
I am not worried about spending 5$ a month for the service, but I miss the option of using the Echo devices to announce notifications.
Is there a way to get that feature within the NabuCasa subscription? And if not, what would be the most secure way of configure the Alexa Media Player from within HACS?
Should I tick/use “Use login method” or “Enable oauth-token app method”?
Do I really need to hand over the keys to the kingdom to just use voice announcements over an Echo device?
For announcements, yes afraid so. You really need the HACS integration if you want to control your Echo speakers from HA. The NabuCasa subscription allows you to control HA entities with Alexa, but not the other way round.
Have you any other speakers? I have voice announcements on Sonos speakers using tts.cloud_say - you need NabuCasa for this too, but you don’t need to give up your Amazon details. As a plus, you can have a male voice and a range of languages and accents.
You can connect to Echos via bluetooth, I did this before the HomePods came out. Once connected you can send TTS through it. For me, all my TTS is done through a Mac using Mac’s built-in capabilities and those can broadcast to all my speakers via airplay, but in your case it could do it via bluetooth.