Whilst I believe the word is often suggestive of a religious or quasi-spiritual context (e.g. "She found herself in communion with nature".), because of its inevitable association with Holy Communion, the OED does recognise, and lists as its first meaning a very general one. (It is only when you get to sense 4, that Holy Communion is mentioned).
1a. The action or fact of sharing or holding something in common with
others; mutual participation; the condition of things so held,
mutuality, community, union.
▸a1382 Bible (Wycliffite, E.V.) (Douce 369(1)) (1850) Ecclus. ix.
20 The comunyoun of deth [L. communionem mortis] wite thou; for in
the myddil of grenes thou shalt gon in.
c1530 Pol. Rel. & L. Poems (1866) 33 Yf thei be merchauntes,
dyvision of heritage is bettyr than commvnion.
1559 T. Paynell tr. Erasmus Complaint of Peace sig. B.iii, I
behold & se the communion of al things a colledge ioyned together, al
one temple, the selfe same lawes, the quotidian & dayly conuentes.
1591 H. Smith Preparatiue to Mariage 2 Mariage..is nothing els but
a communion of life between man and woman, ioyned together according
to the ordinance of God.
1617 F. Moryson Itinerary iii. i. iii. 46 They
attribute..hospitalitie to the Brittanes, communion of all things to
the Normans.
1695 R. South Tritheism 192 To affirm mutual Consciousness to be
the cause of the Union of the Three Divine Persons in the same Nature,
is to confound the Union and Communion of the said Persons together.
1737 D. Waterland Rev. Doctr. Eucharist 272 By Communion, the
Apostle certainly intended a joint-Communion, or participating in
common with others.
1809 S. T. Coleridge Friend 9 Nov. 184 In France there was no
public Credit, no communion of Interests.
1865 G. Grote Plato I. i. 52 Having no communion of nature with
other things.
1921 M. Mortensen Managem. Dairy Plants ii. 11 An association
founded upon a contract between two or more competent persons for
joining their money, goods, labor, and skill..with the understanding
that there shall be a communion of profit among such partners.
1945 J. West Plainville, U.S.A. ii. 100 Each loafing
group..involves a central nucleus of membership, some communion of
interest, and frequently an informal meeting place.
1998 A. J. Nicholls in C. Buffet & B. Heuser Haunted by Hist. xiv.
221 If German statesmen and politicians thought of improving
relations with the West, they usually looked for some illusory
communion of interests with Britain.
The earliest OED reference to Holy Communion with regard to the Eucharist is from 1440 (i.e. in the century prior to the Reformation.
