You know how you often see "Más suim leat.. X Y Z" does this automatically mean that I use "is suim liom" rothaíocht, rith agus snámh" or do you need to say "tá suim agam i..".
Just have to ask as I never seem to hear/see "is suim liom".
I wanted to write "I am interested in bubbles" so can I write "is suim liom boilgeoga"?

I don't think suim is used much in this context, or maybe it is a regional use. I would use spéis in the same places. But if you're hearing suim, maybe that is common over there, and I'd figure that any of them would work.

I have never heard or seen "is suim liom" until now. I don't think it can be used like that. There is something about adjectives and nouns with the copail. Is maith liom (maith - an adjective; literal translation "I consider (something) good") I don't think a noun would work in the same way.

Nouns like suim and spéis require the other "verb to be" i.e. Tá suim agam sa Ghaeilge. Níl spéis dá laghad agam sa rugbaí.

Examples of phrases that are used:

Is aoibhinn liom (an t-amhrán sin.)
Is breá liom an iomáint.
Is gráin liom an éagóir.
Is trua liom na Pailistínigh.
Is fuath liom an foréigean.
Is fearr liom an fuacht ná an bháisteach.
Is maith liom aer úr na farraige cois cladaigh.

If it's an adjective needed, then what about "is suimiúil liom?"

Here are a few uses culled from the dictionaries I have.

to take an interest in something
spéis, suim, a chur i rud

to be interested in something
spéis, suim, a bheith agat i rud

to have no interest in something
ní spéis, suim, liom é

I think the last use is not like "is maith liom", but rather like the possessive.

Quote: [If it's an adjective needed, then what about "is suimiúil liom?"]

Bodhrán, that does sound better than "is suim liom" for sure.

Must add that I have never seen "is suim liom" written anywhere but it was seeing "más suim leat" that made me wonder about it-- with más being a form of the copula I thought then that "is suim" might be possible too but it still seems odd even with the example you give seanw, as in "ní spéis, suim, liom é" (ach tá sé sin an-suimiúil!)

Would that mean more "it is not of interest to me" more so than "I am not interested in it"?

Yep can see now how the adjectives work better with the copula than the nouns Taidhgín, go raibh míle!

Forget about my mentioning nouns and adjectives etc. I can't stand over that.

However I wouldn't write "is suimiúil liom ..." although I think "Is suimiúil nach dtagann Pádraig anseo níos mó" might be used.

That structure is often shortened to one word as follows:

Breá nach ndéanfá iarracht an obair a dhéanamh

and in older texts

Mairg nach bhfuil ina dhúthuata (I am not sure of that one. I think it may be the first line of a poem.)

Trua nach gcoinneofá do chuid airgid. etc.

Just as some verbs are followed by different prepositions / prepositional pronouns [scríobh + chuig; iarr + air; fiafraigh + de; inis + do; etc] and must be learnt by reading the literature or by using a good dictionary -- not a one-word equivalence dictionary -- so also are some nouns associated with particular constructions: Tá slaghdán orm; Cén fuadar atá faoi; Níl suim agam sa teilifís; Bheadh eagla orm roimh iolar; srl.

Good Irish is delicate. Be careful not to force Irish words to follow English and so distort the sentences. Best to read and read and learn by reading rather than by English to Irish translation which can result in ugly constructions unless you are very good at it. Grammatically correct but calculated to clear the bar of Irish speakers.

Well Dinneen's has:

níor shuim liom mo bheo

I no longer valued life.

Actually, I would be more interested in "mo bheo" for "my life". Why not "mo bheatha"?

The only real example of this I can find is this:

"Acht maran suim leat fuath agus tarcuisne thar chuimse do tharraingt anuas ort féin, ná hairigheadh an mháthair óg tú ag tabhairt "it" ar a leinbhín beag gleoidhte."

"But unless you would like to bring hatred and immeasurable scorn on yourself, don't let the young mother hear you call her bonny little child 'it' ".

This from Smaointe fáin an tsuarthamáin, 1938, a translation of Jerome K Jerome's The Idle Thoughts of an Idle Fellow, by Eibhlín Bean Uí Churraoin, from the Waterford Gaeltacht.

there are copula+noun expressions:

is gá liom é
is áil liom
is cuimhin liom
is eagal liom
is gráin liom é
is mian liom
is trua liom é