I don't find anything for "Mitsay" on a web search. Is that a brand? If you look on the back of the keyboard does it give you any other information?

Portuguese layout keyboards I did find show the "=" at exactly the same place as American layouts. 2 keys to the right of the zero key (above the alpha keys).

Left Alt 61 also works for me.

I'd say you probably need to find more information about your keyboard and failing that buy a replacement that has documentation.

it,s a brand of a large electronics salescompany and hasn't anything at back, on the box it says made in Portugal.
cannot experience with the keyboard now, have a no signal on monitor now to resolve. Anyway thanks for your suggestions. P.S. tried to open saved on media work on LibreCalc on W10, but only the first rows apear instead of in the hundred I have on Linux desktop.
miramarcos

If you happen to have a rooted android smart phone you can download USB keyboard app and connect with a USB OTG cable to the PC

dear EzekielProject,
I'm don't know, what do you mean with rooted ? have an android smart phone and what is a USB OTG, I also do have a cable from the Nokia 5 to connect with PC
miramarcos

A rooted phone is one that you've taken control of so you can do what you want with it rather than what the manufacturer or the phone carrier are allowing.

However, I'm not sure why TheEzekielProject suggested you'd need to do it on a rooted phone.

On checking Google play store just now I see free USB keyboard apps available. I haven't tried any of them myself.

The USB Keyboard app I use said that it required root to work, I guess I just assumed that the type of app it is required root. If not, that makes it easier for OP

after I finally could get ubuntu going, after pressing shift with start up, without monitor, I could type in the = sign and could finish my work in LibreCal. Hope tomorrow Asus desktop starts that way, with shift get going again.
miramarcos