Yes, It is safe to use
But Steam Games can be dupes. So be aware. But Lootboy gets you a new key, I gather.
eox1 introduced me to Lootboy. So he is more up-to-date on all ins-and-outs.
LootBoy - die Beute-App für Gamer!
What I do daily on the PC is the "Daily Boost" for some coins.
Then I click in the top-right corner on the diamonds for the "Exploration Quests".
Then I read some comics, now speedreading, 'cause I know all of them, for extra coins.
And I look on "
[Lootboy] Codes for coins/diamonds - Page 383" => you can use some introduction codes (at the top).
I check if there are new codes on the last page. Redeem is top right, the three lines.
When I have 100 diamonds I check out the loot pack with a Steam game in it. It was a real hunt the first time. Good luck!

When you have enough coins you can get a "Lootcoin Lootpack", for 2000 coins. Gives you starter packs, wallpapers, coins, etc.
And regularly an itch.io game and sometimes a Steam key for a game.
-> You can install lootboy also on a tablet. <-
edit @
PurpleGreenTremors: re-reading gives coins again.